Biology - HOT Science Lab

Student
Properties of Water
NGSSS:
SC.912.L.18.12 Discuss the special properties of water that contribute to Earth's suitability as
an environment for life: cohesive behavior, ability to moderate temperature, expansion upon
freezing, and versatility as a solvent. (AA)
Background:
Water is the most common substance on Earth. Nearly three-quarters (about 70 percent) of the
Earth‘s surface is covered with water. Water is unique because it is the only substance that
occurs naturally on Earth in all three states—solid, liquid, and gas. About 2 percent of the
world‘s water is solid, including snow, frost, glaciers, and the polar ice sheet. Less than onethousandth
of a percent of the world‘s water is gaseous, as water vapor. The rest of the world‘s
water is liquid, and can be found in oceans, seas, lakes, rivers, streams, and groundwater.
Sometimes we call water H 2 O. That‘s because water molecules have two hydrogen atoms and
one oxygen atom. While water molecules are neutral as a whole, one end of the water molecule
tends to have a positive charge while the other has a negative charge (polarity). Each end of a
water molecule is attracted to the opposite charged end of another water molecule.
This is called ―hydrogen bonding.‖
Cohesion is the attraction of water molecules to other molecules. It is the result of hydrogen
bonding – the attraction of the hydrogen atoms in water to the oxygen atoms in water. It is the
property that allows water droplets to form. Cohesion is responsible for surface tension. This
property allows some insects to walk across water.
Adhesion is the ability of water to stick to other surfaces. For example, water forms on mirrors in
a steamy bathroom. Adhesion is a property that causes water to be drawn up through soil and
into paper towel. When water is drawn up through small spaces, it is called capillary action.
Water is an amazing substance that is critical to life. It serves a purpose in various processes
such as cellular metabolism, heat transfer, and structural support. For these reasons and more,
the presence of water is a good indicator that life may be sustainable in certain environments,
such as the Jovian moon of Europa.
Problem Statement: What are the properties of water that contribute to living things Or
develop your own problem statement and experiment based on the different properties of water
and its importance to sustaining life on earth (ability to moderate temperature, cohesion, etc.)
Safety: Make sure that the bubble solution is poured on top of trash bags on the tables, report
any spills immediately to the teacher. Use napkins routinely to clean up your lab area.
Vocabulary: polar, nonpolar, adhesion, cohesion, surface tension, capillary action, solvent
Biology HSL Page 231
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